Question

9. If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of
first n terms.


12. Find the sum of the first 40 positive integers divisible by 6.
13. Find the sum of the first 15 multiples of 8.
14. Find the sum of the odd numbers between 0 and 50.

16. A sum of Rs 700 is to be used to give seven cash prizes to students of a school for their
overall academic performance. If each prize is Rs 20 less than its preceding prize, find the
value of each of the prizes.
17. In a school, students thought of planting trees in and around the school to reduce air
pollution. It was decided that the number of trees, that each section of each class will
plant, will be the same as the class, in which they are studying, e.g., a section of Class I
will plant 1 tree, a section of Class II will plant 2 trees and so on till Class XII. There are
three sections of each class. How many trees will be planted by the students?
tres alternately at A and B,​

Answer 1

Answer:

Figure 1 is the clock that shows time 5:40 On its left- sides a mirror is placed and fig 2 is the reflection figure of fig 1

Clearly time seems to be 6:20

Short cut : subtract 5:40 from 12 we get 6:20